1. Field of the Invention
This invention relates to disconnecting switches. More particularly, the invention relates to high voltage air break disconnecting switches and to improvements in their electrical contacts and the bearing used for rotating members.
2. State of the Art
There is a wide variety of high voltage air break disconnecting switches designed for outdoor use. These switches have been given current and voltage ratings along with various other specifications according to construction classifications in American National Standards. Commonly used constructions include single and double side break, vertical break and center break switches.
In all the various constructions, one or both of the contacts making and breaking the circuit are mounted for rotation or pivoting to swing between an open and a closed position. For example, with a single side break switch, one contact is fixed to the end of an arm or switch blade mounted on a rotating insulator to be rotated or swung into contact with a contact on a fixed insulator. The contact on the fixed insulator may pivot or be stationary depending on additional motion that may be imparted to the rotating arm contact.
In the case of a center break switch, both contacts are fixed on arms mounted on insulators which are rotated.
Many innovations have been made over the years in each of the various switch constructions, usually with the improvement applying only to a specific switch construction.
Little has been done in the area of improved bearing support for the rotating members as evidenced by the fact that a large number of switches still use roller bearings which often fuse or melt in a stationary position under current surge/contact corrosion conditions.
Likewise, there has been very little improvements in the area of insuring the maintenance of contact pressure where one of the contact are configured to supply spring pressure. The phosphorus bronze or other spring material used in such contacts losses its spring resilience when overheated due to arcing and heavy momentary current flow thus losing the effectiveness of the contact to further aggravate the arcing and consequent corrosion of the contact.
While multiple contact elements have been used on one or both of the contacts, each element provides only a single point of contact, which if misaligned, breaks the connection causing arcing.